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Pliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.

In our reply we demonstrate the inconsistency of the comment we received from Mazzarini et al. Our data, models and conclusions are solid and framed in the regional evolution of the Northern Apennines, typified by eastward migration of coeval extensional tectonics and magmatism since late Miocene. We show that understanding the natural processes recognizable in the Elba Island requires a scientific approach based on reproducible, reliable and high-quality datasets, independently of the scale of observation.

Recent studies on the stratigraphy of Paleozoic successions belonging to key sectors of the inner Northern Apennines provide data that can be used to propose new hypotheses about the palaeogeography of the western Mediterranean domain during post-Hercynian times. We report here the first evidence of mid- to late Permian (Guadalupian–Lopingian) palynomorphs in the chronostratigraphically highly debated metamorphic units of the Northern Apennines (the Rio Marina Formation, the Mt Calamita Formation and the Le Cetine Formation) and consider the stratigraphic implications for the Tuscan ‘basement’ to which the study rocks belong and their palaeogeographical attribution considering their Gondwana affinity. These results agree with the interpretation that the Alpine Tethyan sedimentary cycle was already active during the mid- to late Permian. Thematic collection: This article is part of the ‘Apennines and Tyrrhenian system’ collection available at: https://www.lyellcollection.org/cc/the-apennines-tyrrhenian-system

Exhumation and cooling of upper crustal plutons is generally assumed to develop in the brittle domain, thus determining an abrupt passage from crystallization to faulting. To challenge this general statement, we have applied an integrated approach involving meso- and micro-structural studies, thermochronology, geochronology and rheological modeling. We have analyzed the Miocene syn-tectonic Porto Azzurro pluton on Elba (Tuscan archipelago – Italy), emplaced in an extensional setting, and have realized that its fast exhumation is accompanied by localized ductile shear zones, developing along dykes and veins, later affected by brittle deformation. This is unequivocally highlighted by field studies and the analysis of microstructures with EBSD. In order to constrain the emplacement and exhumation rate of the Porto Azzurro pluton we performed U-Pb zircon dating and (U+Th)/He apatite thermochronology. It results in a magma emplacement age of 6.4 ± 0.4 Ma and an exhumation rate of 3.4 to 3.9 mm/yr. By thermo-rheological modeling we were able to establish that localized ductile deformation occurred at two different time steps: within felsic dykes when the pluton first entered into the brittle field at 380 kyr, and along quartz-rich hydrothermal veins at c. 550 kyr after pluton emplacement. Hence, the major conclusion of our data is that ductile deformation can affect a granitic intrusion even when it is entered into the brittle domain in a fast exhuming extensional regime.

The Pre-Mesozoic units exposed in the inner Northern Apennines mostly consist of middle-late Carboniferous-Permian successions unconformably deposited on a continental crust consolidated at the end of the Variscan (i.e. Hercynian) orogenic cycle (Silurian-Carboniferous). In the inner Northern Apennines, exposures of this continental crust, Cambrian?-early Carboniferous in age, have been described in the Northern Tuscany, Elba Island (Tuscan Archipelago) and, partly, in scattered and isolated outcrops of southern Tuscany. In this contribution, we reappraise the most significative succession (i.e. Risanguigno Formation) exposed in southern Tuscany and considered by most authors as part of the Variscan Basement. New stratigraphic and structural studies, coupled with palynological analyses, allow us to refine the age of the Risanguigno Fm and its geological setting and evolution. Based on the microfloristic content, the structural setting and the fieldwork study, we attribute this formation to late Tournaisian-Visean (middle Mississipian) time interval and conclude it is not showing evidence of a pre-Alpine deformation. These results, together with the already existing data, allow us to presume that no exposures of rocks involved in the Variscan orogenesis occur in southern Tuscany.

Borgia et al. (2014) illustrated an active volcanic spreading model for the Amiata volcanic area (southern Tuscany, Italy). Although, at first glance, the model may appear appealing, this is not fully supported by the available data and the paper does not take into account their discussion. Accordingly, the supposed negative consequences of the Borgia et al. (2014) model on both contamination of shallow water and geothermal exploitation can likely be regarded as speculative.